Thumb in Front of Harmonica (Part 2)
There's two ways to approach this...
1) Place the right thumb right next to your cheek, still allowing the upper few holes to be open. The bull-horn affect of directing the sound tends to work well, especially if your amp is already very distorted.
2) Place the right thumb on holes 8, 9 and 10 and turn your head to the left so that your thumb touches your cheek and the angle your face makes the cheek cover the holes between the thumb and your mouth (Ex. holes 1-4 covered with mouth for a standard 4 draw tongue block, cheek covers 5-7 and thumb covers holes 8-10). This creates a super-air-tight cup that will make any harmonica player jealous!